Structures such as buildings and bridges are considered a potential target for attack. For example, mechanical cutting is an identified threat against bridge cables, in which a hand-held, rotary or reciprocating blade power saw could be used in an attempt to cut destructively through a cable or other structural element. One approach to protecting bridges is to provide structural hardening for the cable elements in suspension and cable-stayed bridges, including main cables, vertical suspender ropes, and stay cables. One example of a protection system for cables is described in U.S. Pat. No. 8,769,882. Such known cable hardening systems are designed to delay a cutting threat for a given amount of time.
Thermal cutting devices, such as a thermal lance, thermic lance, or exothermic torch, can also be used for cutting steel and concrete and can pose a threat to structures. For example, a thermal lance is formed from a steel tube packed with steel or aluminum rods as a fuel source. Oxygen is pumped through the tube and feeds combustion on the opposite end, where the cutting action occurs. The thermal lance can provide a formidable cutting threat, because of the high temperatures it can attain, for example, between 4950° F. and 8130° F. or even higher, depending on the components and environment. Other thermal cutting devices include a plasma torch, an oxy/acetylene torch, and a petrogen torch.